It is known to use power steering in road vehicles, e.g., electrical power assisted steering, commonly abbreviated as EPAS, in a road vehicle such as a car, lorry, bus or truck, wherein an electric motor assists a driver of the road vehicle by adding an assistive torque to e.g., a steering column or steering rack of the road vehicle.
It is further known to use advanced driver assistance systems, commonly abbreviated as ADAS, such as Lane Keeping Aid systems, commonly abbreviated as LKA systems, in order to help a road vehicle driver maintain the road vehicle in a desired lane. For LKA or lane centering systems where an EPAS is used, a steering wheel torque overlay, i.e., additional steering wheel torque on top of what would have been obtained by the base assist of the EPAS, is used for lateral position control.
However, the need for more advanced autonomous steering functions and also highly autonomous driving (HAD) has put new requirements on current steering safety concepts. One example of such a more advanced autonomous steering function is commonly called Pilot Assist, commonly abbreviated as PA, which helps a driver to drive the vehicle within the road lane whilst at the same time maintaining a preselected time interval to a preceding vehicle.
Highly autonomous driving and advanced driver assistance systems, such as the above described Pilot Assist, adds a requirement of high bandwidth in the wheel angle controller in order for a HAD or PA path wheel/pinion angle request to be tracked fast and accurately.
However, high bandwidth in the wheel angle controller may result in nervous and active steering wheel motions in situations where this behavior is undesirable, for example when driving on a wide lane or on a straight road. In addition to potentially causing discomfort to vehicle occupants this may also be perceived as control of the vehicle being erratic and nervous.
Thus, there is a need for improved solutions which are able to comfortably, calmly and steadily, handle the above requirement for tracking of a HAD or PA path whilst facilitating fulfillment of high Automotive Safety Integrity requirements.